The present invention relates to a new and improved apparatus and method which are used to cushion movement of a member in a machine and to a method of assembling the apparatus.
A known apparatus to cushion movement of a member in a machine is disclosed in U.S. Pat. No. 4,765,227 entitled Die Cylinder Assembly and issued Aug. 23, 1988. The apparatus disclosed in this patent includes a piston which divides a cylinder into upper and lower variable volume chambers. The lower variable volume cylinder chamber is connected in fluid communication with a source of fluid pressure, that is, nitrogen gas. The fluid pressure applied against the lower end of the piston urges the piston to an extended position. When movement of a member in a machine is to be cushioned, the piston is forced downwardly, by the member, against the influence of the nitrogen gas pressure in the lower variable volume chamber of the cylinder.
The operating life of the apparatus disclosed in the aforementioned U.S. Pat. No. 4,765,227 tends to be maximized if seals between the piston and cylinder are lubricated during operation of the apparatus. Systems for lubricating the seals between a piston and cylinder are disclosed in U.S. Pat. No. 4,688,775 issued Aug. 25, 1987 and entitled Self-lubricating Die Cylinder; U.S. Pat. No. 4,691,902 issued Sep. 8, 1987 and entitled Self-lubricating Die Cylinder; and in U.S. Pat. No. 4,815,718 issued Mar. 28, 1989 and entitled Self-lubricating Die Cylinder. The apparatus disclosed in these patents utilize fluid pressure to pump lubricating liquid which is sprayed against surfaces of the piston and cylinder.